The present invention relates to method for machining or turning surfaces of revolution at workpieces preferably at crankshafts, whereby the workpiece is rotated during machining, and wherein a disk-shaped tool that is provided with cutting elements at its circumferential edge for roughing of the workpiece and subsequent finishing of the workpiece is used. The tool for performing the method is provided with cutting elements for the roughing process and with cutting elements for the finishing process.
In the machining of crankshafts it is known from European Patent 0 211 216 and German Offenlegungschrift 35 23 274 to perform a roughing process of the crankshaft by radially plunge-cutting by turning with a formed cutter. Subsequent to this roughing process, the finishing process of the crankshaft is performed by turning broaching in which the crankshaft is rotated at a relatively high speed while the disk-shaped tool is rotated at a relatively low speed. For each individual width of a crankshaft pin, special cutters for the turning broaching of the finishing process must be employed since the cutting edges extend at an angle relative to the axis of rotation of the tool and furthermore must be embodied in a dished fashion. The cutting elements which must be special ordered are manufactured only in small quantities and are provided with only two cutting edges. Correspondingly, the cutting element costs for the broaching turning step of the finishing process are high. In order to produce cylindrical pins, the tool must further be provided with complicated plate seats for the cutting elements used for the broaching turning process. During broaching turning the cutting edges penetrate at a very great negative angle into the crankshaft resulting in very high normal forces. This results in an increased wear at the cutting edges of the cutting elements and in an increased bending of the crankshaft during the turning broaching process. As a consequence, during broaching turning processes a rattling tendency is observed which leads to a reduced accuracy of the cutting process. Furthermore, during the machining of steel in a turning broaching process long, curled cuttings are produced which inhibit a reliable flow of cuttings within the tool and the machine. Especially with automated machines the removal of these long, curled cuttings is difficult and expensive. These long, curled cuttings furthermore differ considerably with variations of the excess material to be removed.
It is therefore an object of the present invention to provide a method and a disk-shaped turning tool of the aforementioned kind in which as the cutting elements commercially available cutting plates that are made of various cutting materials may be employed and with which the workpiece may be machined during the finishing operation such that at low cutting material costs and with a reliable removal of cuttings a high precision cutting of the workpiece may be accomplished, while low cutting pressures will be generated.